Practical Skills

Question 1

What is an independent variable

Answer 1

This is the characteristic or condition you change intentionally to observe the effect on the dependent variable

Question 2

What is a dependent variable

Answer 2

This is the phenomenon or condition you aim to observe or measure as a result of the experiment.

Question 3

What is a controlled variable

Answer 3

This is the condition kept constant to ensure that changes in the dependent variable are due to the manipulation of the independent variable

Question 4

What is differential staining

Answer 4

This is when multiple stains are used and each stain binds to a specific cell structure, staining each structure differently so the structure can be easily identified

Question 5

What does acetic orcein do

Answer 5

It binds to DNA and stains chromosomes red

Question 6

What does eosin do

Answer 6

Eosin stains cytoplasm dark red or pink

Question 7

What does iodine do

Answer 7

Iodine stains starch blue-black (appears violet under the microscope)

Question 8

What does iodine in potassium iodide solution do

Answer 8

It stains cellulose yellow

Question 9

What does haematoxylin do

Answer 9

Stains RNA/DNA a purple/blue colour

Question 10

What does methylene blue do

Answer 10

It is an all-purpose stain often used to stain DNA blue

Question 11

How do you mount a wet mount sample

Answer 11

this is used for a variety of live specimens, such as aquatic animals
Use a pipette to put a drop of water on the slide.
Use tweezers to place the specimen in the water.
Put the cover slip on by standing it upright on the slide, next to the water droplet, then carefully tilt it down onto the specimen. Be careful to not add bubbles – these will obstruct the view of the image.
Add a stain. Put a drop on one edge of the cover slip. Put a paper towel on the opposite edge. The paper towel will absorb the stain, drawing it under the coverslip, staining the specimen. (You want to make sure the stain used is not toxic to the live specimen)

Question 12

How to mount a dry sample

Answer 12

this is used for specimens such as hairs, parts of insects, pollen, parts of flowers etc.
Slice the specimen into a thin piece so light can pass through
Use tweezers to pick it up and put it in the middle of the slide
Put a cover slip on top of it.

Question 13

How do you calculate the actual length of the species being measured

Answer 13

the number of divisions should be multiplied by the length of one division (you calculated this when you calibrated the graticule).

Question 14

How do you calibrate a graticule

Answer 14

1. Set up the microscope to the required magnification to view the sample.
2. Place a stage graticule on the stage.
3. Line up the two scales (the stage and eyepiece graticules) similar to the diagram.
4. Count the number of divisions on the eyepiece graticule equivalent to each division on the stage micrometre.
5. As the length equivalent to each division on the stage micrometer are known, it is possible to calculate the length of one eyepiece division.

Question 15

What are the rules for drawings

Answer 15

● No shading. Areas that should be shaded should be labelled instead.
● The drawing should take up at least half of the page.
● Label lines must be completely horizontal, drawn with a ruler, exactly touch the object that they’re labelling and must not overlap each other.
● Drawing lines should completely connect and should not be broken
● A scale should be given e.g. for the magnification of the image size.
● They should be drawn in pencil and look like the actual image.

Question 16

How do you identify the four main vessels attached to the heart during dissection

Answer 16

Identify the four main vessels attached to the heart. Arteries are thick and rubbery, whereas veins are thinner. Identify the coronary artery on the external surface. Locate where the coronary artery connects to the aorta

Question 17

How do you cut across a stem

Answer 17

You cut the section as perpendicular to the length of the stem as possible and as thinly as possible

Question 18

What colours does toluidine blue stain tissues

Answer 18

Phloem- red
Xylem- green/blue-green
Sclerenchyma- blue-green/sometimes green
Collenchyma- red-purple
Parenchyma- red-purple

Question 19

What colour is toluidine blue in non-lignified tissue and lignified tissue

Answer 19

Non-lignified: pink/purple
Lignified: green/blue

Question 20

When examining a kidney, what is the renal capsule covered in

Answer 20

It is covered in renal capsule

Question 21

What is below the renal capsule

Answer 21

The cortex

Question 22

Which part of the kidney is indented

Answer 22

The renal hilium

Question 23

What are the tubes

Answer 23

The renal vein, renal artery and the ureter

Question 24

Which tube is likely to have the most adipose (fatty) tissue

Answer 24

The ureter

Question 25

How does the cortex appear

Answer 25

It appears dense and grainy and it is a lighter shade than the medulla

Question 26

What are the renal pyramids

Answer 26

These are the many cone-shaped structures in the medulla. They appear stripy because they contain straight sections of the nephrons (loops of Henle and collecting ducts)

Question 27

What are in between the renal pyramids

Answer 27

Renal columns

Question 28

What are renal calyces

Answer 28

These are the hollow cavities visible leading from the base of the renal pyramids

Question 29

What are renal pelvis

Answer 29

Large hollow structure that connects to the ureter

Question 30

What is random sampling

Answer 30

This is where sample sites are selected randomly

Question 31

What are the advantages of random sampling

Answer 31

This prevents selective sampling,ensuring the data is not biased

Question 32

What are the limitations of random sampling

Answer 32

Not all the areas/types of habitat may be sampled equally, leading to inaccurate data. Also, species with a small population may be missed, leading to an underestimate of biodiversity

Question 33

What is a stratified sampling (non-random sampling)

Answer 33

In this method, the habitat is divided into groups that appear different, and each area is sampled separately. Each group should be mutually exclusive (each population can only be in one group) and collectively exhaustive (no population must be left out).

Question 34

What are the advantages of the stratified sampling

Answer 34

This ensures that all areas are sampled and prevents small populations from being missed out. It also allows areas of different population levels in the same habitat to be sampled equally

Question 35

What are the disadvantages of stratified sampling

Answer 35

This may lead to some over-representation of some areas in the study, for example small areas may be sampled more than necessary because they look different from other areas.

Question 36

What is opportunistic sampling

Answer 36

This method is when areas are chosen to sample by the researcher either using their prior knowledge, or choosing areas that interest them as they are collecting data.

Question 37

What are the advantages of opportunistic sampling

Answer 37

This is easier and quicker than random sampling and produces more data

Question 38

What are the disadvantages of opportunistic sampling

Answer 38

This method has a potential for bias. Species which are more noticeable may be included more often than less noticeable species, leading to an overestimation of their importance, and an inaccurate estimate of biodiversity.

Question 39

What is systematic sampling

Answer 39

This is when samples are taken at set distances e.g.using a transect

Question 40

What are the advantages of systematic sampling

Answer 40

This is good to view a change in biodiversity or population along a line

Question 41

What are the disadvantages of systematic sampling

Answer 41

This method has the risk of missing species as only a small area is sampled. This could cause biodiversity to be underestimated

Question 42

What is species diversity

Answer 42

This is a measure of the number of different species in a given community

Question 43

What is a community

Answer 43

A community is the sum of the populations of different species living in the same place and time

Question 44

Is simpson’s index of diversity

Answer 44

D=1-[sum of(n/N)^2]

Question 45

What is species abundance

Answer 45

This is a measure of the amount of a certain in a specific habitat

Question 46

What is species distribution

Answer 46

Species distribution is a measure of where species are located / how species are distributed

Question 47

When investigating the effect of temperature on catalase activity, what are the independent and dependent variables

Answer 47

Independent variable= temperature Dependent variable= rate of reaction

Question 48

When investigating the effect of enzyme (amylase) concentration on the rate of reaction, what are the independent and dependent variables

Answer 48

Independent variable= the concentration of amylase (enzyme concentration) Dependent variable= rate of reaction

Question 49

When starch is present what colour does iodine solution change to

Answer 49

It turns dark blue-black when starch is present but remains orange-brown when there’s no starch

Question 50

When investigating the effect of substrate concentration on the rate of an enzyme-controlled reaction, what are the independent and dependent variables

Answer 50

Independent variable= the concentration of hydrogen peroxide (substrate concentration) Dependent variable= rate of reaction

Question 51

How does serial dilution occur

Answer 51

Most methods of serial dilution have a factor of 2, meaning with each dilution the concentration halves. 1. Set up 5 boiling tubes 2. Starting with a 2.00% catalase solution, add 4cm^3 to the first boiling tube. 3. Using a syringe, add 2cm^3 of the solution in the first tube to the next tube. This makes a 1.00% catalase solution 4. Repeat this process to make 0.50%, 0.35% and 0.13% solutions. Each successive solution is half the concentration of the previous one.